错误1215:使用ON DELETE SET NULL时无法添加外键约束

Question

我正在尝试在MySQL中创建以下表.第一个:

CREATE TABLE IF NOT EXISTS address(
  address_id INT NOT NULL AUTO_INCREMENT,
  address_region VARCHAR(10) NOT NULL,
  address_country VARCHAR(20) NOT NULL,
  address_city VARCHAR(30) NOT NULL,
  PRIMARY KEY(address_id))ENGINE = InnoDB;

我成功创建了它,但是当我尝试创建另一个表时如下

CREATE TABLE IF NOT EXISTS spot(
  spot_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
  spot_address INT(11) NOT NULL,
  spot_name VARCHAR(50) NOT NULL,
  spot_desc VARCHAR(500) DEFAULT ' ',
  spot_speadd VARCHAR(100) NOT NULL,
  spot_viewtime INT DEFAULT 0,
  FOREIGN KEY(spot_address)
  REFERENCES address(address_id)
  ON DELETE SET NULL
  ON UPDATE SET NULL);

我收到一个错误:

ERROR 1215(HY000):无法添加外键约束

为什么这个create table语句失败了？

Answer 1

您在表中有NOT NULL约束,然后尝试将其设置为在父表中删除或更新.spot_addressspotNULLaddress